Asking that question even casually is a sure-fire way of enlivening a soiree that counts at least a few ardent record collectors among its guests.

Eventually, and probably sooner than later, eavesdroppers on the provoked conversation will hear two names - those of Arturo Toscanini and Wilhelm Furtwängler - displace mention of all others. If the makeup of the discussants is at all representative of the general musical population, it's likely that opinion on the virtues of these two legendary maestros will be sharply divided; if liquid refreshments have sufficiently lowered inhibitions, it's likely that a defense of one of them will be augmented by an attack on the other, that the attack will be vehemently parried and even more vehemently countered, that the spinoff arguments will reach into such touchy areas as generalized artistic sensibilities, political persuasions and attitudes about the ''meaning'' of life. Onlookers will witness passions rise and tempers flare; it will be an interesting entertainment, even for the partygoers who don't really give a hoot about music.

From 1928 to 1936 Toscanini was music director of the New York Philharmonic, and for the last 17 years of his career he conducted the much-loved NBC Symphony Orchestra. Thus Toscanini's spirit has never been far from American listeners, and in the last several years it's almost been made incarnate through the efforts of the American-based RCA company to publish or republish practically everything he did within earshot of a recording device.

To put it simply, Toscanini was a literalist, an objective interpreter who felt it his obligation to realize as precisely as possible only what the composer had notated. His detractors would call him cold and mechanical, a mere technician devoid of feeling.

The most recent reading of Beethoven's familiar Symphony No. 5 that I'd encountered was something I'd hit upon on the radio, a recently recorded version by some conductor and orchestra whose names I immediately forgot - there was no reason to remember them, because the interpretation, while perfectly decent, was in no way different from most of the dozen and a half other interpretations of this piece I'd heard in the last year.

But of the lot, it was Toscanini and Toscanini alone who was billed as the greatest conductor.

So successful was the advertising campaign that, in the 1930s and '40s, vast numbers of people who never heard an instant of any of Toscanini's performances believed the superlative to be true.

Among musical connoisseurs, Toscanini was indeed respected, even revered. For the masses, it was simply taken for granted that Toscanini was the world's greatest conductor who led the world's greatest orchestra almost exclusively in the greatest imaginable interpretations of the world's greatest musical masterpieces.

It happened in America. Some would say it could have happened only in America. And probably they would be right.

Whether the characteristically American canonization of a foreign-born maestro was a good thing or a bad thing remains open to debate.

On one hand, it's true that during Toscanini's tenure as music director of the NBC Symphony (1937-54) the herculean efforts of the public relations people at the network and at its affiliate record company - RCA Victor - helped win for classical music a wider audience than it had ever had before in this country. But it's at least arguable that the emphasis on the ''greatness'' of Toscanini and his repertoire seriously stifled the growth of that audience. Toscanini may be the reason why American orchestras these days are as technically proficient as they are; Toscanini may also be the reason that American audiences these days are by and large composed of musical dullards.

The negative approach - one to which I admit being sympathetic - is taken by Joseph Horowitz in his new ''Understanding Toscanini'' (Knopf; $30).

This is a fascinating book that is likely to raise the hackles of all who examine it. It deals exhaustively with Toscanini, his career and his recorded legacy. But its primary subject matter - its target - is the musical cultism that sprang up with Toscanini and to a large extent continues to exist in this country.

An enormous amount of research and thought went into this 472-page essay. So, apparently, did a lot of venom. Horowitz, a 38-year-old former New York Times music critic who now deliberately avoids events at Lincoln Center, sets a pugnacious tone with his subtitle: ''How He (Toscanini) Became an American Culture-God and Helped Create a New Audience for Old Music.'' Then he comes out swinging, and he doesn't back off until the very end, when he relaxes into a fantasy about how the salvation of music in America rests with a new generation of listeners somehow immune to hype. He retains his credibility, though, when he suggests that his ''closing whiff of optimism'' might be just, after all, pro forma.

This book should prove interesting even to self-proclaimed music lovers who really believe that the only works worth hearing are masterpieces by dead composers. At the very least, it offers a good explanation of why certain aspects of American culture are the way they are.

When the United States was founded by immigrants, the first generations were simply too busy surviving to indulge themselves much in the pleasures of sophisticated art forms. It was only after the new nation was firmly established that Americans could afford to enhance their lives, if they so chose, with so-called High Culture. But by that time - after centuries of laudable hard work and perseverance in the face of adversity - most Americans had little familiarity with High Culture. Because with few exceptions it didn't really exist on their own soil, those who wanted it looked homeward, to Europe. Of necessity, High Culture had to be imported, and with it came a curious mixture of anti-intellectualism and inferiority complex.

In the chapter labeled ''Setting the Stage,'' Horowitz quotes liberally from Mark Twain's 1869 ''The Innocents Abroad,'' a travelogue in which Twain sarcastically derides the stuffiness of European culture while at the same time aspiring to know that culture more intimately. The section contains an ungentle, but apt, reference to the Missouri state motto. ''Mark Twain's 'show me' attitude betrayed him,'' Horowitz writes. ''He used his heresies to subvert the awe he felt but did not want to show. His insistence on a modern, democratic New World as the measure of all things registered some innocence, but also willful naivete.''

The same chapter deals at length with the career of P.T. Barnum, a Twain contemporary whose knack for catering to America's collective ''willful naivete'' earned him a fortune. Horowitz concentrates on Barnum's handling, in 1850, of the American debut tour of the Swedish soprano Jenny Lind. Barnum did it for the sake of prestige, to rid himself of his reputation as humbug artist. Yet he promoted the tour with all the humbug artistry he possessed.

Barnum knew that Americans would not pay good money just to hear a singer. But he guessed - and guessed correctly - that they would pack the halls if that singer were in effect guaranteed to be the greatest in all of Europe. For months before her arrival, Barnum promoted Lind for all she was worth. The American media bought it, and so did the American public. Lind was a fine singer, but as Barnum admitted, ''she was a woman who would have been adored even if she had had the voice of a crow.''

''The bigger the humbug, the better the people like it,'' Barnum said. It was a pragmatic philosophy, and - as Horowitz tells the story - it was a philosophy shared by the man who hired Toscanini in 1937 to lead the new NBC Symphony.

Not that there was anything shady about David Sarnoff's motives. Indeed, the founder of the broadcasting empire was something of an altruist who as early as 1924 stated that one of radio's obligations was to be a ''unifying force'' by which ''the supreme music, education and entertainment of the country'' would be disseminated. Toscanini had been fabulously successful during his eight years (1928-36) as music director of the New York Philharmonic. When the idea for a top-quality broadcast orchestra was born, it seemed obvious that Toscanini would have to be recruited - at whatever cost - to be the orchestra's leader.

Sarnoff got Toscanini for $40,000 a year. It was a good deal, for - as Fortune magazine reported in its January 1938 issue - the contract was a coup that promised to ''make NBC the biggest corporate name in music.'' The prediction came true, but largely because the NBC-RCA public relations machine worked so hard to make Toscanini the biggest individual name in music.

Horowitz's book does nothing to detract from Toscanini's still-legendary fame; the chapter titled ''Toscanini on Records'' is a superb example of sharply focused performance reviewing, and its bottom-line assessment is that Toscanini was indeed ''an unquestionably great conductor.''

What irks Horowitz - and what irks me - is the way the concept of ''greatness'' in music was given the hard sell by the NBC and RCA flacks. Implicit in all the broadcast commentaries and in all the advertisements was this message: Toscanini is the greatest conductor; the greatest conductor conducts, of course, only the greatest music; therefore, if Toscanini doesn't conduct it, it's not the greatest, and if it's not the greatest, then it's not worth the attention of a real red-blooded American music lover.

It's a sick syllogism. But apparently it offered self-conscious Americans an appealing form of aesthetic security. Toscanini's narrow and very conservative repertoire was marketed as the blue chip stock of music. An emotional investment in a Toscanini-certified masterpiece was a safe investment, the announcers suggested. Just by tuning in or by buying a record, they in effect said, you, too, can experience gr-r-reat music, right in your own home. And you don't even have to think about it. Or even really listen.

The idea that great music could be absorbed with effort was fostered in Toscanini's heyday by proponents of what music critic Virgil Thomson once not very affectionately called ''the music appreciation racket.''

Along with Thomson's, Horowitz cites the opinion of Theodor Adorno on those musical tour guides who do no more than point out themes and who would place ''the unspeakable horn melody from the slow movement of Tchaikovsky's Fifth'' on the same level as ''the climaxes of Beethoven's Seventh Symphony.'' Listeners who subscribe to this approach - ''the ideal of Aunt Jemima's ready-mix for pancakes extended to the field of music'' - have their sensibilities arrested ''at the infantile stage,'' Adorno said. ''Their primitivism is not that of the undeveloped, but that of the forcibly retarded.''

Horowitz's own attack on non-thinking masterpiece worshippers is perhaps not so brilliant as is Adorno's. But it is just as forceful, and it is sustained through the entire length of ''Understanding Toscanini.''

Herbert von Karajan actually died last week. Some of his fans probably had assumed this would never happen. Karajan - conductor, yachtsman, jet pilot, skier, race-car driver, fashion plate, multimillionaire - was 81, and for the last few years he'd been suffering from a spinal condition that made walking both difficult and painful. Still, there was an air of invulnerability about this white-haired Austrian maestro, a quality of steely strength that gave the impression he would go on forever.

Thoughts on reincarnation occupy the final paragraph of Roger Vaughan's 1986 biography of the conductor. ''I am so serious I can't even discuss it,'' Karajan told Vaughan. ''I like what Goethe wrote about this. He said, if I have so many things to think, to do and to meditate upon, and my body refuses to follow me, then nature must give me another one. Must give me another. Not maybe.''

The forceful demand was the essence of Karajan's career. All it took for something to become reality was a declaration from on high. Extra rehearsals, a different set of soloists, a new concert hall, more vacation time, a bigger salary, whatever - if Karajan wanted it, he got it. For him to state that nature must give him another body was not out of character; if his staff could have arranged it, it would have been done. Who knows? Perhaps they're working on it right now.

On the other hand, perhaps the staff is relieved that the Karajan era has finally ended. He could not have been an easy man to work for. And controversy hounded him almost from the start.

After piano studies at the Mozarteum in his native Salzburg, Karajan joined the conducting staff of the Vienna State Opera. Five years later, he was still an unknown underling there, but the situation changed when, in 1929, he was invited to lead a performance of ''The Marriage of Figaro'' in the small German city of Ulm. It was in Ulm that Karajan's famous ''take charge'' attitude - a dictatorial attitude that touched on all aspects of the business at hand - first manifested itself. The engagement led immediately to his appointment as music director of the Ulm theater, and during the ensuing five seasons his successes were increasingly grand.

Karajan's next position was in Aachen, another small German city. He accepted the music directorship in September 1934, but first he signed up with the Nazis. According to Vaughan's biography, Karajan claimed he joined the Nazi Party just prior to the appointment in Aachen. It was no big deal, he said, just one of those things a person sometimes has to do in order to get a certain job.

''Before me was this paper, which stood between me and almost limitless power and a budget to provide for an orchestra with which I could do however many concerts I liked, including tours,'' he told Vaughan. ''I had a secretary, an office, I was in heaven. And they were saying that I must be a member, that maybe I would have to do a concert for them once in a while, that's all. So I said what the hell, and signed.''

Archival evidence shows, however, that Karajan joined the Nazi Party not in Aachen in 1934 but in his hometown of Salzburg on April 8, 1933, just two months after Hitler's rise to power in Germany and five years before the German invasion of Austria. Precisely why he became a card-carrying Nazi at such an early date is unknown; confronted by Vaughan with photocopies of his original membership papers, Karajan simply dismissed them as fabrications. The issue is clouded further by the fact that in 1942 Karajan married a woman whose grandfather was Jewish. But no matter when he joined, or why, Karajan was a Nazi. And his loyalties paid off.

In 1941 he was fired from the position in Aachen because he spent too much time guest-conducting elsewhere in Hitler's Reich; one of the orchestras with which he performed most frequently was the prestigious Berlin Philharmonic. After the war, Karajan hid out for a while in Italy and then went through a two-year period of de-Nazification. Although officially forbidden to work during this time, he nevertheless managed to conduct at the Salzburg Festival, in Lucerne and in Vienna. Following his ''rehabilitation,'' his career took off like a shot.

In 1947 he made his debut with the Philharmonia Orchestra in London. The next year he began a long relationship with the La Scala opera house in Milan. In 1950 he began making recordings with both the Vienna Philharmonic and the London Philharmonia; in 1951 he took on Wagner's entire ''Ring'' cycle at the Bayreuth Festival; in 1955 he succeeded Wilhelm Furtwängler as music director of the Berlin Philharmonic, with the added twist that his title was ''conductor for life.'' In 1956 he was appointed artistic director of the Salzburg Festival; in 1957 he became director of the Vienna State Opera and principal conductor of the Vienna Philharmonic.

Everywhere he went, there were protests against his Nazi affiliation, and many world-class soloists - Isaac Stern, for example, and later Itzhak Perlman - let it be known that they would never perform in tandem with him. But these obstacles hardly slowed his progress. In the early 1960s, with the major concert and opera performances in Vienna, Salzburg and Berlin firmly under his control and his recording activities with the Deutsche Grammophon label well under way, Karajan was nicknamed ''Generalmusikdirektor'' of all Europe.

There is more to Europe than just the German-speaking countries, of course, yet the sobriquet comes close to being accurate. Karajan might not have been the director of everything, but his influence was widespread and potent. Even after 1964, when he disassociated himself from the Vienna State Opera, he wielded far more clout than any other individual in the arts world.

''Before me was this paper, which stood between me and almost limitless power . . . .'' It's a telling sentence. Karajan offered it to biographer Vaughan as his excuse for joining the Nazi Party. But we can read it as the key that explains the entire Karajan phenomenon.

Politics have little to do with music. Power, on the other hand, has a great deal to do with music, especially when one is considering the work of an orchestral conductor. A conductor is, more than anything else, a leader. Musical knowledge and interpretive insight might be listed among a conductor's assets, but they count for nothing unless he is somehow able to make the players do his bidding. Sweet-talking an orchestra into going along with him won't do the trick. Whether he gains it through respect or through brute force, the conductor has to have firm command over all that happens both in rehearsals and in concerts.

How much power is too much power?

When it focuses solely on music, the question is moot. Karajan obviously exerted immense power over the musicians in his Berlin Philharmonic. There is much to quibble about regarding Karajan's interpretations: their blandness, their lack of depth and passion, their homogeneity, their inevitable smoothing out of passages the composers intended to sound rough. But there is no denying the sheer perfection of the Berliners' sound under Karajan's baton. Because he had genuine authority over what they did with their instruments, Karajan made his orchestra the most polished in the entire world, bar none. His power seems to have been absolute, but it was not excessive.

When the question is applied to a conductor's administrative power, however, limits can be seen. And many players in the self-governing Berlin Philharmonic felt that Karajan over-stepped the boundaries, that he had more power than he - or any other human being - deserved.

The troubles surfaced most recently in 1982, triggered by Karajan's flat-out demand that 23-year-old clarinetist Sabine Meyer be hired even though the members of the orchestra felt her sound and style did not fit in with their own. When the orchestra refused to capitulate, Karajan announced that he was single-handedly suspending all of the Philharmonic's recording, touring and festival activities. Cowed, the orchestra agreed to offer Meyer a one-year probationary contract. Meyer knew she wasn't welcome, so she quit before the contract expired. Karajan publicly blamed the orchestra members for driving her away; to punish them, he canceled one of their concerts at the Salzburg Festival and - at his own considerable expense - brought in the rival Vienna Philharmonic to perform.

In spite of the humiliation, and in spite of the bad blood that had long flowed between Karajan and his musicians, the city fathers of West Berlin - who support the orchestra to the tune of $25 million per year - refused to challenge the maestro's ''conductor for life'' appointment. Karajan was their most valuable resource, and he knew it. Even his bitterest enemies were surprised when, in April of this year, he resigned. Karajan said he packed it in because of his ailing back. Some observers of the Berlin scene say he quit because he was fed up with flak generated a year earlier when a member of the Berlin city council dared to question the validity of Karajan's cancellation of several concert dates.

In any case, Karajan's alleged medical problems did not prevent him from conducting rehearsals for the Verdi opera that is set to open the 1989 Salzburg Festival on Thursday of this week; he put in a full day's work on July 15 and then the next day had his fatal heart attack.